Dual-mode oscillator for stress compensated cut resonator

Abstract

Both parallel-type and serial-type dual-mode oscillators employing stress compensated cut resonators having various configurations are disclosed. Both classes of dual-mode oscillators employ multiple tank circuits to pass one frequency of the resonator and block the other frequency. The tank circuits isolate the operation of the two oscillator sub-circuits that form the dual-mode oscillator from one another. The dual-mode oscillators may be implemented with either bipolar or CMOS transistors. The parallel-type dual-mode oscillators employ inverters to provide gain. The serial-type dual-mode oscillators employ a two (or three) stage design including a follower circuit first stage and an inverting amplifier/limiter circuit second stage, with an optional intervening transimpedance amplifier stage.

The invention claimed is: 
     
       1. A parallel-type dual-mode oscillator comprising:
 a resonator, the resonator adapted to resonate at a lower frequency F 1  and an upper frequency F 2 ; 
 a first oscillator sub-circuit adapted to operate at the lower frequency F 1 , the first oscillator sub-circuit including:
 a first input tank circuit, the first input tank circuit coupled to the resonator, the first input tank circuit adapted to pass the lower frequency F 1  and to block the upper frequency F 2 ; 
 a first inverter, the first inverter coupled to the first input tank circuit, the first inverter adapted to invert a signal from the first input tank circuit; and 
 a first output tank circuit, the first output tank circuit coupled to the first inverter and the resonator, the first output tank circuit adapted to pass the lower frequency F 1  and to block the upper frequency F 2 ; 
 
 a second oscillator sub-circuit adapted to operate at the upper frequency F 2 , the second oscillator sub-circuit including:
 a second input tank circuit, the second input tank circuit coupled to the resonator, the second input tank circuit adapted to pass the upper frequency F 2  and to block the lower frequency F 1 ; 
 a second inverter, the second inverter coupled to the second input tank circuit, the second inverter adapted to invert a signal from the second input tank circuit; and 
 a second output tank circuit, the second output tank circuit coupled to the second inverter and the resonator, the second output tank circuit adapted to pass the upper frequency F 2  and to block the lower frequency F 1 ; and 
 
 a third tank circuit, the third tank circuit coupled to the resonator in parallel, the third tank circuit in parallel with the resonator adapted to have a capacitive impedance at the lower frequency F 1  and at the upper frequency F 2 . 
 
     
     
       2. The parallel-type dual-mode oscillator of  claim 1 , wherein the first input tank circuit and the first output tank circuit each includes:
 a first leg in parallel with a second leg; 
 wherein the first leg includes in series:
 a first capacitor; and 
 a first inductor; and 
 
 wherein the second leg includes in series:
 a second capacitor; and 
 a second resistor. 
 
 
     
     
       3. The parallel-type dual-mode oscillator of  claim 2 ,
 wherein a series combination of the first capacitor and the first inductor is adapted to resonate at the lower frequency F 1 ; and 
 wherein a series combination of the first capacitor and the first inductor in parallel with the second capacitor is adapted to resonate at the upper frequency F 2 . 
 
     
     
       4. The parallel-type dual-mode oscillator of  claim 1 , wherein the second input tank circuit and the second output tank circuit each includes:
 a first leg in parallel with a second leg; 
 wherein the first leg includes in series:
 a first capacitor; and 
 a first inductor; and 
 
 wherein the second leg includes in series:
 a second inductor; and 
 a second resistor. 
 
 
     
     
       5. The parallel-type dual-mode oscillator of  claim 4 ,
 wherein a series combination of the first capacitor and the first inductor is adapted to resonate at the upper frequency F 2 ; and 
 wherein a series combination of the first capacitor and the first inductor in parallel with the second inductor is adapted to resonate at the lower frequency F 1 . 
 
     
     
       6. The parallel-type dual-mode oscillator of  claim 4 , wherein the second leg further includes a second capacitor in parallel with the second inductor. 
     
     
       7. The parallel-type dual-mode oscillator of  claim 1 , wherein the third tank circuit includes in series:
 a first inductor; and 
 a first resistor. 
 
     
     
       8. The parallel-type dual-mode oscillator of  claim 1 , wherein one or more of the first input tank circuit, the first output tank circuit, the second input tank circuit, or the second output tank circuit includes a trimmable capacitor. 
     
     
       9. The parallel-type dual-mode oscillator of  claim 1 , wherein the upper frequency F 2  is within approximately 10% of the lower frequency F 1  or the upper frequency F 2  is an odd integer multiple of the lower frequency F 1 . 
     
     
       10. A serial-type dual-mode oscillator comprising:
 a resonator, the resonator adapted to resonate at a lower frequency F 1  and an upper frequency F 2 , a parasitic frequency F 3  corresponding approximately to an average of the lower frequency F 1  and the upper frequency F 2 ; 
 a first oscillator sub-circuit adapted to operate at the lower frequency F 1 , the first oscillator sub-circuit including:
 a first tank circuit, the first tank circuit coupled to the resonator, the first tank circuit adapted to pass the lower frequency F 1  and to block the upper frequency F 2 ; 
 a first follower circuit, the first follower circuit including a first node coupled to the first tank circuit, a second node, and a third node; 
 a third tank circuit, the third tank circuit coupled between the second node of the first follower circuit and ground, the third tank circuit adapted to allow amplifier/limiter gain at the lower frequency F 1  and to shunt the parasitic frequency F 3  to ground; and 
 a first inverting amplifier/limiter circuit, the first inverting amplifier/limiter circuit coupled between the second node of the first follower circuit and the third node of the first follower circuit, the first inverting amplifier/limiter circuit adapted to amplify and limit a signal at the third node of the first follower circuit; 
 
 a second oscillator sub-circuit adapted to operate at the upper frequency F 2 , the second oscillator sub-circuit including:
 a second tank circuit, the second tank circuit coupled to the resonator, the second tank circuit adapted to pass the upper frequency F 2  and to block the lower frequency F 1 ; 
 a second follower circuit, the second follower circuit including a first node coupled to the second tank circuit, a second node, and a third node; 
 a fourth tank circuit, the fourth tank circuit coupled between the second node of the second follower circuit and ground, the fourth tank circuit adapted to allow amplifier/limiter gain at the upper frequency F 2  and to shunt the parasitic frequency F 3  to ground; and 
 a second inverting amplifier/limiter circuit, the second inverting amplifier/limiter circuit coupled between the second node of the second follower circuit and the third node of the second follower circuit, the second inverting amplifier/limiter circuit adapted to amplify and limit a signal at the third node of the second follower circuit. 
 
 
     
     
       11. The serial-type dual-mode oscillator of  claim 10 , wherein the first tank circuit and the fourth tank circuit each includes:
 a first leg in parallel with a second leg; 
 wherein the first leg includes in series:
 a first capacitor; and 
 a first inductor; and 
 
 wherein the second leg includes in series:
 a second capacitor; and 
 a second resistor. 
 
 
     
     
       12. The serial-type dual-mode oscillator of  claim 11 ,
 wherein, for the first tank circuit, a series combination of the first capacitor and the first inductor is adapted to resonate at the lower frequency F 1 ; and 
 wherein, for the first tank circuit, a series combination of the first capacitor and the first inductor in parallel with the second capacitor is adapted to resonate at the upper frequency F 2 . 
 
     
     
       13. The serial-type dual-mode oscillator of  claim 11 ,
 wherein, for the fourth tank circuit, a series combination of the first capacitor and the first inductor is adapted to resonate at the parasitic frequency F 3 ; and 
 wherein, for the fourth tank circuit, a series combination of the first capacitor and the first inductor in parallel with the second capacitor is adapted to resonate at the upper frequency F 2 . 
 
     
     
       14. The serial-type dual-mode oscillator of  claim 10 , wherein the second tank circuit and the third tank circuit each includes:
 a first leg in parallel with a second leg; 
 wherein the first leg includes in series:
 a first capacitor; and 
 a first inductor; and 
 
 wherein the second leg includes in series:
 a second inductor; and 
 a second resistor. 
 
 
     
     
       15. The serial-type dual-mode oscillator of  claim 14 ,
 wherein, for the second tank circuit, a series combination of the first capacitor and the first inductor is adapted to resonate at the upper frequency F 2 ; and 
 wherein, for the second tank circuit, a series combination of the first capacitor and the first inductor in parallel with the second capacitor is adapted to resonate at the lower frequency F 1 . 
 
     
     
       16. The serial-type dual-mode oscillator of  claim 14 ,
 wherein, for the third tank circuit, a series combination of the first capacitor and the first inductor is adapted to resonate at the parasitic frequency F 3 ; and 
 wherein, for the third tank circuit, a series combination of the first capacitor and the first inductor in parallel with the second capacitor is adapted to resonate at the lower frequency F 1 . 
 
     
     
       17. The serial-type dual-mode oscillator of  claim 14 , wherein the second leg further includes a second capacitor in parallel with the second inductor. 
     
     
       18. The serial-type dual-mode oscillator of  claim 10 ,
 wherein each of the first follower circuit and the second follower circuit includes one of a bipolar transistor follower circuit, a metal oxide semiconductor field effect transistor (MOSFET) follower circuit, or a compound-transistor follower circuit; and 
 wherein the compound-transistor follower circuit includes:
 a first MOSFET of a first type adapted to have an M P1 =1; 
 a second MOSFET of the first type adapted to have an M P2 >1; and 
 a third MOSFET of a second type opposite the first type. 
 
 
     
     
       19. The serial-type dual-mode oscillator of  claim 10 ,
 wherein the first inverting amplifier/limiter circuit and the second inverting amplifier/limiter circuit each includes a corresponding transimpedance amplifier; and 
 wherein one or more of the first tank circuit, the second tank circuit, the third tank circuit, or the fourth tank circuit includes a trimmable capacitor. 
 
     
     
       20. The serial-type dual-mode oscillator of  claim 10 , wherein the upper frequency F 2  is within approximately 10% of the lower frequency F 1  or the upper frequency F 2  is an odd integer multiple of the lower frequency F 1 .